AN ASSESSMENT OF CONVENTIONAL RANS TURBULENCE MODELS TO RESOLVE THE AIRFLOW OVER AIRCRAFT ENGINE INLETS AT HIGH ANGLES OF ATTACK
Leonardo Costa Almeida1; Bruno Souza Carmo1; Luis Gustavo Trapp2
1 Escola Politécnica da Universidade de São Paulo; 2 EMBRAER - Empresa Brasileira de Aeronáutica S.A.
doi:10.20906/CPS/COB-2015-1061
Resumo
The flow over nacelle inlets plays a crucial role in the correct operation of the aircraft. One of the main issues regarding engine inlets is the flow separation which can occur at high angle-of-attack operations. Inlet distortion arises from these conditions and can cause fan and compressor instabilities, reducing the amount of thrust generated by the engine and compromising overall aircraft efficiency and performance. Compressor surge and stall can also occur along with structural issues due to eventual blade resonance, increasing values of actual stress and reducing fatigue life. Due to safety reasons, it is crucial to be able to accurately predict the performance of the engine throughout the aircraft operating envelope. This paper presents an investigation of numerical methodologies to simulate using computational fluid dynamics the flow over subsonic engine inlets operating at takeoff conditions, featured by low freestream Mach numbers and high angles of attack. Steady three-dimensional Reynolds-Averaged Navier-Stokes equations were solved using the commercial code CFD++. Three different turbulence models (Realizable k-epsilon, Spalart-Allmaras and k-omega SST) were assessed as to their capability to evaluate important flow features. For each model, results show distortion levels at the fan face, pressure recovery, pressure distribution along the lip, peak surface Mach number and separation angle. The numerical investigation was supported by previous wind tunnel test data performed on a long-duct nacelle of a commercial aircraft.
Palavras-chave: Nacelle; Separation; Distortion; CFD